1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image by operating a plurality of image forming units, an initial adjustment method for the image forming apparatus, and a computer readable medium recording a program for causing the image forming apparatus to perform initial adjustment.
2. Description of the Related Art
An image forming unit constituting an image forming apparatus includes, as an important unit, an imaging unit. The imaging unit generally includes a charger, a photoconductor, a development roller, a developer agent, a cleaning unit and the like. An imaging unit that includes a two-component developer agent in which toner and carrier are mixed has a TCR (Toner/Carrier Ratio) sensor for detecting the concentration ratio between toner and carrier.
Generally, the photoconductor and/or the developer agent slightly deteriorate every time image formation is performed, and ultimately, the quality of an image formed by the imaging unit starts to deteriorate. When the deterioration in the image quality reaches an unacceptable level, the user determines that the members constituting the image forming unit (such as the photoconductor and the developer agent) has reached their end of life and replaces the members.
Recently, an image forming apparatus of which imaging unit itself is replaced for simplifying the replacement works has commonly been used. When a TCR sensor is contained in the imaging unit, the TCR sensor is also replaced with a new TCR sensor at the same time when the imaging unit is replaced. When the TCR sensor is arranged on the image forming apparatus side, the replacement may cause shift in the positional relationship between the TCR sensor and the imaging unit due to assembly tolerance or the like.
That is, due to the replacement of the imaging unit itself or the change in the positional relationship between a detection target in the imaging unit and the TCR sensor, the detection performance of the TCR sensor may become different between before and after the replacement of the imaging unit. Accordingly, when replacing the imaging unit, it is necessary to perform an initial adjustment in order to agitate toner in the imaging unit and/or to adjust the TCR sensor. In other words, the purpose of the initial adjustment is to correct for variation in concentration due to the replacement of the photoconductor and/or the developer agent and to correct for color drift due to the replacement of the imaging unit, i.e., to stabilize an image.
As a method of performing the initial adjustment, for example, Japanese Laid-Open Patent Publication No. 08-087213 discloses an image forming apparatus in which, when it is determined that it is a state where the apparatus is installed based on a machine-new-status value indicative of the state of the apparatus, after a hopper is supplied with toner, an initialization process (a NEW unit sequence), which is a process performed when each unit is new, is performed. With such an image forming apparatus, the initialization process at the installation is automated, whereby the burden of the user is largely reduced.
Japanese Laid-Open Patent Publication No. 2003-241590 discloses an image forming apparatus in which a during-initial-setting-operation flag is set for determining whether or not an initial setting operation of a new process cartridge is completed. In the image forming apparatus, firstly, before a new process cartridge is attached to a new image forming apparatus, for example, before the image forming apparatus is shipped from the factory, the during-initial-setting-operation flag is set in advance to an initial-setting-operation-not-completed state. Thereafter, the new process cartridge is attached to the image forming apparatus. Then, when the main power supply of the image forming apparatus is turned on, the initial setting operation of the process cartridge is performed. Here, until the initial setting operation normally ends, the during-initial-setting-operation flag is maintained to be the initial-setting-operation-not-completed state. When the initial setting operation normally ends, the during-initial-setting-operation flag is set to an initial-setting-operation-completed state.
Japanese Laid-Open Patent Publication No. 2001-005344 discloses an image forming apparatus in which, for each color of magenta (M), cyan (C), and yellow (Y), image stabilizing control that can be executed in monochrome mode is executed in monochrome mode and not basically executed when switching the mode, whereby the time of image stabilizing control when switching the mode is reduced.
Japanese Laid-Open Patent Publication No. 2001-066842 discloses an image forming apparatus in which, when printing is performed in monochrome mode, firstly, it is determined whether or not the timing of executing an image stabilizing adjustment in monochrome mode has come, based on whether or not the number of image forming times Nm in monochrome mode is not less than threshold value N2. If the timing has come, then whether or not an original for which an image is to be formed is monochrome is checked and the number of pages Ne thereof is counted. When it is expected that printing in color mode will be performed before the next timing of the image stabilizing adjustment in monochrome mode comes, an image stabilizing adjustment in color mode is performed even if it is during printing in monochrome mode.
Japanese Laid-Open Patent Publication No. 2001-092196 discloses an image forming apparatus in which, when timing of an image stabilizing adjustment has come when monochrome mode is set, firstly, the number of image forming times M in monochrome mode before entering next color mode and threshold value N for determining the timing of the image stabilizing adjustment are compared with each other. If M≦N, then based on that image formation in color mode is to be performed before the timing of next image stabilizing adjustment, flag F=1 is set so that the image stabilizing adjustment in color is performed in advance. If N<M, then only when M≦2N and the number of image forming times L in monochrome mode after previous image formation in color mode (including formation of a reference pattern of the image stabilizing adjustment) is greater than prescribed value P, flag F=1 is set so that the charging state of color toner is recovered in advance.
Past image forming apparatuses before the above-described image formation apparatuses were proposed employed a scheme in which a serviceman or the user performed the initial adjustment with an operation screen or the like, instead of including means for detecting replacement of the imaging unit. The image forming apparatuses employing such a scheme were often of the type in which replacement of the imaging unit was carried out by a “service engineer” or a “special user trained as a manager of the apparatus”. Such image forming apparatuses were configured to allow the “service engineer” to perform the initial adjustment by a special operation with the operation screen so that general users did not inadvertently perform the initial adjustment.
However, recently, color image forming apparatuses have been in wide use owing to their reduced price, for example, and therefore it has increasingly been necessary for a general user to replace the imaging unit. Accordingly, image forming apparatuses automatically performing the initial adjustment by identifying whether or not the initial adjustment of the imaging unit has already been performed have been coming into common use.
In the color image forming apparatus for use by a general user, color printing is less frequently performed as compared with the color image forming apparatus for professional use. Therefore, the life of the color imaging units and that of the color image forming apparatus itself are often approximately the same. This is because the user hopes to suppress the printing costs and does not perform all printing in color even with the color image forming apparatus. That is, since the color imaging units wear less (less frequently used) than the black imaging unit, the life of each color imaging unit is often longer than that of the black imaging unit. In the color image forming apparatuses of most users, the life of each color imaging unit is longer than that of the color image forming apparatus. Thus, such a user replaces the black imaging unit only until the end of the life of the color image forming apparatus.
That is, in most color image forming apparatuses, the color imaging units are not replaced until the end of the color image forming apparatus. The color imaging units are replaced only in a color image forming apparatus of a user who requires far greater pages to be printed in color relative to the average color printing pages/monochrome printing pages ratio, and/or in a failed color image forming apparatus. For example, provided that the printing yield (machine life) of an image forming apparatus is 200,000 pages and that of each imaging unit is 40,000 pages, and used by a person who performs color printing at the ratio not more than 20%, the color imaging units will not be replaced. On the other hand, the black imaging unit will be replaced four times, except for the first setup.
Under the circumstances, in order to reduce the costs for the color imaging units, an image forming apparatus has been realized in which a user can perform the initial adjustment of the color imaging units with an operation panel or the like while nonvolatile memory for storing information as to whether or not the initial adjustment has been completed is omitted from each color imaging unit. In such type of image forming apparatus, only the black imaging unit of which replacement frequency is relatively great includes nonvolatile memory for allowing the image forming apparatus to recognize whether or not the initial adjustment has been completed, and based on that recognized information, the initial adjustment is automatically performed.
On the other hand, such an image forming apparatus involves the following problems. In a general initial adjustment of the imaging unit, after an automatic adjustment of the TCR sensor is performed, image stabilizing work for adjusting color drift, tone reproduction and the like is performed. More specifically, when the user sets all imaging units to the image forming apparatus, the image forming apparatus obtains information as to whether or not an initial adjustment of the black imaging unit has already been completed from nonvolatile memory of the black imaging unit. Then, after the initial adjustment of the initial adjustment of the black imaging unit is completed, a serviceman or the like activates an initial adjustment window of each color imaging unit with the operation panel, so that initial adjustment of each color imaging unit is performed.
That is, the initial adjustment is automatically performed for the black imaging unit for which information as to whether or not the initial adjustment has already been completed is stored, the initial adjustment must be manually performed for the color imaging units.
When the black imaging unit and the color imaging units each have nonvolatile memory for detecting information as to whether or not the initial adjustment has been completed, the image forming apparatus is allowed to recognize which imaging unit has its initial adjustment completed. Therefore, all of the imaging units can automatically have their initial adjustment (in particular, the agitation process) performed substantially at the same time. However, the above-described omission of the detection means from the color imaging units limits activation conditions for performing the initial adjustment, and the initial adjustment must be separately performed for the black imaging unit and for the color imaging units. Thus, the time required for the initial adjustment is increased. In particular, since the agitation process requires several minutes to be completed, the imaging units that require agitation must start the agitation process at the same time, or inconveniently the initial adjustment takes enormous time.